JPH03289253A - Telephone conference equipment - Google Patents

Abstract

PURPOSE:To prevent invasion of line noise into a conference speech circuit by controlling an insertion loss set in a variable loss circuit in response to digital quantity corresponding to an analog quantity resulting from rectifying and smoothing a line noise invaded from an input channel and an output channel of the 4-wire side of a 2/4-wire conversion circuit. CONSTITUTION:A control circuit 6 eliminates a loss Li of a variable loss circuit 7 when the presence of a voice signal is discriminated in a signal inputted from a communication line and controls the voice signal so as not to be attenuated. Similarly, when the absence of the voice signal is discriminated, the loss is included. That is, the loss Li inserted to the variable loss circuit 7 is decided as equation Li=Vn-Va (Li>=0), where Vn is a line noise memory level and Va is a preset signal level data. Thus, the loss proportional to the line noise level is set to the variable loss circuit 7. Thus, the invasion of the line noise into a conference speech circuit is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial field of application to which the invention pertains The present invention relates to a telephone conference device that connects a plurality of telephones via a communication line and conducts a conference call between multiple points. .

(2) Conventional technology When making a conference call between multiple points by connecting communication lines, the conventional method is to have conference participants add human signals from other lines other than their own line and send them back. be. FIG. 4 shows a block diagram of a conventional conference call circuit. In the figure, l
2 is an audio input/output terminal, 2 is a 2-wire to 4-wire conversion circuit, and 3 is an audio signal addition/distribution circuit. During a conference call, the audio input signal input from the communication line is sent to the audio input/output terminals 1 and 2 wires.
The signal is inputted to an addition/distribution circuit 3 via a four-wire conversion circuit 2. The addition/distribution circuit 3 outputs the audio input signal to all lines except the line where the audio input signal is manually input.

Therefore, the audio uttered by a conference participant can be heard by all participants. -Generally, in addition to the above-mentioned audio input signal, line noise is also input from the communication line. In addition to induced noise that mixes into the communication line, this line noise includes ambient noise that is collected by the microphone of the telephone and output to the communication line when a public address telephone is used as a terminal of a conference call device. This also includes the case where it is input to the teleconference device as line noise.

In conventional conference call circuits, the line noise input from the communication line is added and distributed by the addition/distribution circuit 3 in the same way as the voice input signal, which deteriorates the S/N ratio in the conference call circuit and reduces the clarity of the call. decreases.

In particular, when making a conference call by connecting multiple communication lines, such as with a teleconferencing device, if even one of the connected communication lines has a high line noise level, the line noise level may be high. The S/N ratio of the entire conference call circuit will deteriorate, and the effect on the conference call quality will be very large.

(3) Purpose of the Invention The present invention was made in view of the above-mentioned problems, and provides a telephone conference device that can prevent line noise generated manually from a communication line from entering the conference call circuit. The purpose is to provide

(4) Structure and operation of the invention In order to achieve this object, the telephone conference device of the present invention has two wires for each communication line for a plurality of connected two-wire communication lines.
A 4-wire conversion circuit is connected, and an addition and distribution means for adding the audio signals of conference participants input from the communication line and distributing the same to the communication line again is arranged on the 4-wire side of the 2-wire to 4-wire conversion circuit. In a telephone conference device that performs a conference call between multiple points by A configuration comprising a control circuit that controls an insertion loss amount set in the variable loss circuit in accordance with a digital amount corresponding to an analog amount obtained by rectifying and smoothing line noise mixed from the line side human power communication path and the output communication path. have.

FIG. 1 shows an embodiment of the present invention. FIG. 2 is a circuit diagram showing an example of a clear stream smoothing circuit used in the present invention, and FIG. 3 is a flow chart showing the circuit operation of the present invention. In FIG. 1, l is an audio input/output terminal, 2 is a 2-wire to 4-wire conversion circuit,
3 is an addition/distribution circuit, 4 is a manual communication path, 5 is an output communication path,
6 is a noise detection control circuit, 7 is a variable loss circuit, 8 is a rectification smoothing circuit, and 9 is an analog/digital conversion circuit (hereinafter referred to as A/
10 is a control circuit. In FIG. 1, an audio human input signal input from a communication line is input to an audio input/output terminal 1.2-wire to 4-wire conversion circuit 2. The input communication path 4 and the variable loss circuit 7 are added and distributed by the addition/distribution circuit 3, and the output communication path 5. 2-wire to 4-wire conversion is performed for all communication lines except the communication line to which the same audio signal is input. It is output via the circuit 2 and the audio input/output terminal 1.

Here, the line noise detection operation will be explained with reference to the flowchart of FIG. 3. The audio input signal input from the communication line is 2 wires.
4-wire conversion circuit 2. Rectifying and smoothing circuit 8 via input communication path 4
It is rectified and smoothed by

The signal level of the rectified and smoothed audio input signal is determined by the A/D
The conversion circuit 9 converts the analog quantity into a digital quantity, and the control circuit 10 reads it. Similarly to the audio input signal, the audio output signal level of the output communication path 5 output to the communication line is also sent to the control circuit 1 via the rectifying and smoothing circuit 8 and the A/D conversion circuit 9.
0 (Sl). The control circuit 10 is composed of a microcomputer or the like. The control circuit IO controls the line noise memory level Vn to increase or decrease as follows, assuming that the line noise memory level prepared in advance is Vn and the read human input signal level is Vl.

b) When Vi-Vn≧0 (S6) Set the line noise memory level Vn to a predetermined value. It is increased slowly with a time constant (S7).

Tl) When Vi-Vn<0 (S6) Set the line noise memory level Vn to a predetermined value. It is rapidly decreased with a time constant (S9).

By controlling the increase/decrease of the line noise memory level as described above, it is possible to detect the steady line noise level manually input from the communication line without being affected by the temporally changing (inflected) voice signal. I can do it.

FIG. 2 shows an example of the rectifying and smoothing circuit 8 using a logarithmic compression circuit for either the input communication path 4 or the output communication path 5. In FIG. In FIG. 2, II is the input channel 4 or the output channel Ip! i
Input terminal connected to channel 5, 12 operational amplifier, 13
is a rectifier diode, 14 is a capacitor, 15 is a resistor,
Reference numeral 16 indicates an output terminal to the A/D conversion circuit 9 at the next stage. The audio signal input from the input terminal 11 is sent to the operational amplifier 12.
is logarithmically compressed, then rectified by diode 13, smoothed by capacitor 14 and resistor I5, and output terminal 1.
Output from 6.

In a conference call circuit using a 2-wire to 4-wire conversion circuit 2 as shown in FIG.
Sometimes it goes around. In order to prevent the aforementioned line noise detection operation from malfunctioning due to such a loop signal, the line noise memory level Vn is increased/decreased as follows. That is, the read audio signal levels of the input communication path 4 and output communication path 5 are set as Vi and V, respectively.
When o is set (Sl), a) When vi≧Vo, it is determined that a voice signal has been input manually from the communication line, and the circuit loss circuit 7 performs increase/decrease control on the line noise memory level Vn (82 to S).

r: J) In the case of Vl ku vO The detected input communication path 4 signal is No audio signal is input from the line If the loop signal from output communication path 5 The variable loss circuit 7 determines that Increase/decrease in line noise memory level Vn Control is stopped (S2.Sl., S,).

Next, to explain specifically, if the loss amount is still set in the variable loss circuit 7, not only the line noise but also the audio input signal input from the communication line will be attenuated in the same way. , the control circuit 10 needs to be controlled to remove the set loss amount Li of the variable loss circuit 7 when the audio output is performed manually from the communication line. Determination as to whether or not an audio signal has been input from the communication line is performed as follows.

First, each signal level Vo of the output communication path 5 and input communication path 4 is
and vl are detected and compared, and it is determined whether the detected signal is from the input communication path 4 or the signal input from the communication line (S2).
. Next, if it is determined that the input signal is from a communication line, it is determined whether or not the human input signal includes a voice signal using the following equation based on the line noise memory level Vn and the human input signal level Vi.

b) If Vi-Vn≧α, there is an audio input signal (YES
) (S3).

D) If Vi-Vr+<α, NO without audio input signal
) (S3).

Here, α is a predetermined value.

Next, a method of controlling the insertion loss amount of the variable loss circuit 7 by the control circuit 6 will be explained. When the control circuit 6 determines that there is an audio signal in the signal input from the communication line according to the above equation, the control circuit 6 removes the loss amount Li of the variable loss circuit 7 in step S4.
), the audio signal is controlled so as not to be attenuated. Similarly, if it is determined that there is no audio signal, the amount of loss is included (S8).

That is, assuming that preset signal level data is Va for the line noise memory level Vn, the loss amount Li to be inserted into the variable loss circuit 7 is determined as follows.

Li=Vn-Va However, Li≧0(S8) By calculating the insertion loss amount Li of the variable loss circuit 7 using the above formula, the loss amount proportional to the line noise level is set in the variable loss circuit 7. It becomes (S5). Here, the line noise memory level Vn is set by performing amplification processing according to the input call voice signal level Vi as follows (
s6).

b) When Vi-Vn≧O Slowly increase Vn (s7).

mouth) When Vi-Vn<0 Rapidly decrease Vn (S,).

For example, if the line noise level is high, a large amount of loss will be set in the variable loss circuit 7, so the circuit noise input from the communication line will be attenuated by the variable loss circuit 7 and suppressed to below a predetermined level. It will be done. Therefore, line noise is no longer added and distributed within the addition/distribution circuit 3 like the voice input signal, and is not output to other communication lines.

1. In step S2, if the audio signal is not input manually from the communication line (NO), the insertion loss amount Li is added (S , .), the amount of loss is set proportional to the line noise level (S, .).

(5) As described in detail, according to the present invention, it is possible to prevent line noise from entering the conference call circuit, thereby improving the clarity of the conference call and making it easier to hear. It is possible to provide a telephone conference device that is easy to use and has high call quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a conference call circuit according to the present invention, FIG. 2 is a circuit diagram showing an example of a rectifying and smoothing circuit used in the present invention, and FIG. 3 is a flow chart showing the circuit operation of the present invention. FIG. 4 is a block diagram showing an example of a conventional conference call circuit. 1... Audio input/output terminal, 2... 2-wire to 4-wire conversion circuit, 3... Addition/distribution circuit, 4... Human power communication path, 5... Output communication path, 6... Noise Detection control circuit, 7... Variable loss circuit, 8... Rectification and smoothing circuit, 9... Analog/digital (A/D) conversion circuit, 1
0...Control circuit, 11...Input terminal, 12...
・Operation amplifier, 13... Rectifier diode, 14
...Capacitor, 15...Resistor, 16...
Output terminal.

Claims (1)

[Claims] For a plurality of connected two-wire communication lines, each communication line has two
A line-to-four-line conversion circuit is connected to the four-line side of the two-to-four-line conversion circuit, and an addition and distribution means for adding and distributing audio signals of conference participants input from the communication line to the communication line is connected to the four-line side of the two-to-four line conversion circuit. A telephone conference device that performs a conference call between multiple points by placing the variable loss circuit in the 4-wire side input communication path of the 2-wire to 4-wire conversion circuit, and the 2-wire to 4-wire conversion circuit. comprising a control circuit for controlling an insertion loss amount set in the variable loss circuit according to a digital amount corresponding to an analog amount obtained by rectifying and smoothing line noise mixed from the input communication path and the output communication path on the 4-wire side. A telephone conference device featuring: